A gas separation method includes supplying a mixed gas to a zeolite membrane complex and permeating a high permeability gas through the zeolite membrane complex to separate the high permeability gas from other gases. The mixed gas includes a high permeability gas and a trace gas that is lower in concentration than the high permeability gas. The molar concentration of a first gas included in the trace gas in the mixed gas is higher than the molar concentration of a second gas included in the trace gas in the mixed gas. The adsorption equilibrium constant of the first gas on the zeolite membrane is less than 60 times that of the high permeability gas. The adsorption equilibrium constant of the second gas on the zeolite membrane is 400 times or more that of the high permeability gas.

A gas separation method includes supplying a mixed gas to a zeolite membrane complex and permeating a high permeability gas through the zeolite membrane complex to separate the high permeability gas from other gases. The mixed gas includes a high permeability gas and a trace gas that is lower in concentration than the high permeability gas. The molar concentration of a first gas included in the trace gas in the mixed gas is higher than the molar concentration of a second gas included in the trace gas in the mixed gas. The adsorption equilibrium constant of the first gas on the zeolite membrane is less than 60 times that of the high permeability gas. The adsorption equilibrium constant of the second gas on the zeolite membrane is 400 times or more that of the high permeability gas.

Methods and systems for producing vinyl acetate may use flammability limit (FL) formulas with improved efficiencies at more than one location in the vinyl acetate production process. Herein, FLs can be used at one or more of four portions of the vinyl acetate production process: the reactor, the process-to-process heat exchangers, the carbon dioxide removal system, and the ethylene recovery system. Such FLs are functions of operating conditions and include at least one interaction term that represents the interrelation of two or more of the operating conditions (e.g., temperature, pressure, and component concentration) on the FL.

Methods and systems for producing vinyl acetate may use flammability limit (FL) formulas with improved efficiencies at more than one location in the vinyl acetate production process. Herein, FLs can be used at one or more of four portions of the vinyl acetate production process: the reactor, the process-to-process heat exchangers, the carbon dioxide removal system, and the ethylene recovery system. Such FLs are functions of operating conditions and include at least one interaction term that represents the interrelation of two or more of the operating conditions (e.g., temperature, pressure, and component concentration) on the FL.

A method for producing a shell catalyst which comprises, in the outer shell, one or more of the following metals: Pd, Pt, Ag and Au. Also the use of the shell catalyst produced using the method according to the invention for the production of vinyl acetate monomer, in the hydrogenation of hydrocarbons, in particular the selective hydrogenation of polyunsaturated hydrocarbon compounds, or in the oxidation of alcohols to ketones/aldehydes/carboxylic acids.

A method for producing a shell catalyst which comprises, in the outer shell, one or more of the following metals: Pd, Pt, Ag and Au. Also the use of the shell catalyst produced using the method according to the invention for the production of vinyl acetate monomer, in the hydrogenation of hydrocarbons, in particular the selective hydrogenation of polyunsaturated hydrocarbon compounds, or in the oxidation of alcohols to ketones/aldehydes/carboxylic acids.

Methods of producing gold-palladium catalysts suitable for use in the production of vinyl acetate may include drying the catalyst after the incorporation of a promoter at higher temperatures (e.g., 160° C. or greater) to restructure the metals and/or alloys on the catalyst. The restructured catalyst advantageously has increased catalytic activity and improved stability.

Methods of producing gold-palladium catalysts suitable for use in the production of vinyl acetate may include drying the catalyst after the incorporation of a promoter at higher temperatures (e.g., 160° C. or greater) to restructure the metals and/or alloys on the catalyst. The restructured catalyst advantageously has increased catalytic activity and improved stability.

Ion chromatography may be used for measuring the concentration of metal ions in various streams of a vinyl acetate production process. For example, a method may comprise: reacting ethylene, oxygen, and acetic acid in the presence of a catalyst and optionally a catalyst promotor like sodium acetate and/or potassium acetate to yield a crude vinyl acetate stream; measuring a concentration of a metal ion of the crude vinyl acetate stream and/or a stream downstream thereof with an ion chromatograph, wherein the metal ion is selected from the group consisting of Group I metal ions, Group II metal ions, transition metal ions, and any combination thereof.

Ion chromatography may be used for measuring the concentration of metal ions in various streams of a vinyl acetate production process. For example, a method may comprise: reacting ethylene, oxygen, and acetic acid in the presence of a catalyst and optionally a catalyst promotor like sodium acetate and/or potassium acetate to yield a crude vinyl acetate stream; measuring a concentration of a metal ion of the crude vinyl acetate stream and/or a stream downstream thereof with an ion chromatograph, wherein the metal ion is selected from the group consisting of Group I metal ions, Group II metal ions, transition metal ions, and any combination thereof.